Experts in the area are familiar with the large number of people who are affected by a cornea pathology known as keratoconus. The term “keratoconus” is derived from two Greek terms “kerato” (cornea) and “konos” (cone). It is a condition in which the normal shape of the cornea is distorted and develops a deformation in the shape of a cone that changes and progressively alters the patient's vision, making it ever more blurry. The disease process depends on the age of the patient and the onset of symptoms. Normally, the younger the patient and more precipitous the onset of keratoconus symptoms occurs, the more rapid the progress; it always presents bilaterally and asymmetrically, either owing to congenital alterations or provoked through weakness in the corneal tissue (corneal surgery or previous trauma).
In the present day different treatment modalities are known, depending on the degree and corneal deformation process, these are listed here below:                glasses in the early stages        contact lenses if glasses are no longer effective        intracorneal rings when the eye develops an intolerance for contact lenses and there is evidence of disease progression        Cross-linking, or ultraviolet light treatment to halt the progress of keratoconus        corneal transplant in more advanced stages of keratoconus and in cases where other options do not offer any hope of improvement (for example, corneal scarring, and very advanced keratoconus).        
Exactly as has been shown, in the early stages the patient can use glasses. Nevertheless, when the disease progresses, the narrowing and deformation of the cornea causes a high irregular stigmatism that cannot be treated with glasses. In these cases it is important to use hard contact lenses that improve vision even if they do not halt the progression of the keratoconus, making surgery the only option for stopping the progressive deformation of the cornea. Cross-linking treatment is effective in stopping the evolution of keratoconus, can still be used in cases where there is good corneal thickness.
In light of this, determined implantable prostheses have been developed to be used in those cases where the disease has progressed to the point where the treatments discussed earlier are effective; these prostheses achieve many more practical outcomes for the patient. These prostheses consist of longitudinal segments in arc configurations that are implanted by using intrastromal tunnels both to guide the segments and for those that are affixed. These tunnels vary as much in width as in internal and external diameter, depending on the characteristics of the prosthesis.
At present, four design types of implants are used:                triangular section segments: a section in the form of an isosceles triangle with different arc longitudes and thicknesses.        trapezoid section segments: a section in the form of a triangle truncated at the top;        hexagonal section segments: a section with six corners and        oval section segments: a transverse section with oval configuration            In all cases the previously mentioned segments that use current techniques, longitudinal arched bodies have openings that facilitate the insertion of a segment inside the corneal tunnel by use of a Sinskey hook. The elasticity of corneal tissue tends to cause problems with segment implantation. Additionally, segment manufacture uses milling and the material used is PMMA (polymethacrylate), without external buffing which means that the quality of the finished product is determined by the wear of the diamond tool that is used.
All this, together with the limitations of the software used in manufacture, makes the mechanization of the segment difficult, some of which are the following:                fractures during handling;        deposit of materials on the inside of the hole and consequent infection risk.        Need to use Sinskey Hooks: risk of scratching the intrastromal layers and causing infections        poor angulation for an easy implantation of the segment.Milling of PPMA:            The excessive use of the diamond produces poor finished products with risks of fracture or deposits with consequent infection risks.Software Limitations:    Impossibility of using free software that permits the production of all segments desired.
There are two established techniques for manufacturing intrastromal tunnels: manual and laser. Manual technique employs various instrumental tunnelizing materials manufactured in titanium and a diamond knife. The tunnelizing instruments do not so much cut as they delaminate intrastromally to create a tunnel, which incurs a high risk of perforation and in some cases requires the use of a suction console to keep the eye in a fixed position while the tunnel is being created. Complications that can arise with the manual technique are wide incisions, infections, tunnel asymmetry, deposits in the tunnel and post-operative trauma, among others.
In the case of femtosecond laser techniques, the laser provides pulses of intrastromal energy that causes a separation of the lamellae and creates a tunnel and the prosthesis entry incision. This technique provides several advantages over the manual technique since it is more sterile, less traumatic, provides exact depth without diameter limitation and less post-operative trauma among others.
When the possibilities offered by existing technology as covered in this brief commentary are taken into account, and the characteristics identified with each one, the present invention has as its primary objective the development and creation of an intrastromal segment for implantation in intrastromal tissue, concretely in the patient's cornea, through exclusive application of laser technology that allows us to eliminate at least a good part of the inconveniences and disadvantages that have been outlined above, and that implements a surgery that is the least traumatic possible, and with the least possible risk of causing complications. This goal is fully realized in the intrastromal segment that will be the described in what follows, whose principal characteristics appear summarized in the features portion of claim 1 annex.
In essence, the intrastromal segment proposed by the invention is conceived of as a longitudinally elongated body of variable dimensions according to each concrete need, designed for implantation by means designed for use with it. In contrast to known techniques, the segment of the present invention offers a configuration of noticeably rounded hubs devoid of any communicating openings that facilitate placement, with the consequent elimination of complications posed by these openings (see above discussion), and which also incorporates marks on one of their bases, optimally three marks on the narrowest base that allow correct positioning of the segment, and of these the centre mark is used as a reference point to know where the segment should go and when it is in position, thus also acting as a symmetrical reference point for the arc longitude. Additionally, and to avoid losing the segment or inverting it, the segment is put into place using a disposable implantation guide, but usable during the implantation stage, which connection allows the segment to be readied for implantation.
In this way, although with the use of laser techniques for creating the tunnel, segment tunnel implantation using the former techniques requires breaking the insertion process down into a series of phases that include a) in case where forceps are used, the extraction of the segment from the case, which already causes a certain level of difficulty owing to the form of the sections of the main segment (triangular, trapezoidal, hexagonal, oval) and therefore correspondingly demands an increased level of precaution and care; to introduce the segment with forceps through the incision with special care in cases of very thin segments to avoid inverted positioning of it that causes bad vision and should require new surgery; to open the incision and introduce the segment without causing it to move or jump in such a way as to position itself in the cornea with risk of infection, or causing deposits in the segment; it must be introduced entirely with tweezers while avoiding any movement of the patient's eye to keep the segment from jumping thereby requiring the surgery to be redone and in so doing creating additional risk of leaving deposits that could produce an infection or difficulty in introducing the segment into the tunnel in the case in which small fibres interpose themselves inside of the bridge, which would require the prosthesis to be removed and the bridge to be smoothed with the help of the tunnelling instrument, or of manual surgery for the posterior reintroduction of the segment, with the consequent traumatisation and stress on the cornea owing to the location and the force entailed, or (b) in the case where segment tunnel implantation is envisioned using a Sinskey hook, consistent in one instrumental piece that is introduced through the opening in the segment and finishes by implanting it, in which case the segment should be distanced from the incision to avoid risks of infections and that the incision might seal over in the future. The hook should be equipped with a titanium tip, not rounded, but sharp, which may result in trauma to the cornea if scratching should occur to the tissue, and which has the disadvantage that the segments must be handled by the openings themselves which are weak and may break when handled with the hook, requiring it to be replaced by a new one if it has not yet been introduced, and if it has, requiring a new incision to be made from the opposite side that would allow it to be handled. Each new incision would, of course, entail risks of perforation and infection, a danger that the invention segment avoids completely due to the formal and structural characteristics found in the disposable positioner (disposable guide track) that has been conceptualized and described in the preceding, and to the instrumental developed for an efficient handling of the segment, in particular the implanting mechanism that substitutes efficiently for the present methods, (and which is the object of a separate registration under the title of the same applicant).